Geovisualizing land degradation risk in Southeast Brazil Using remote sensing and GIS-based assessment
Discussion of land degradation patterns
The finding that stable land conditions dominate the study area (68.4%) aligns with national-scale analyses of Brazilian land cover, which show that despite intense historical pressure, significant portions of the landscape persist as stable natural vegetation or managed agricultural land13. The most significant stable classes—Unmanaged Areas with Agriculture and Forest Potential, collectively represent nearly half (48.7%) of the total landscape and constitute the region’s primary reservoir of productive and ecological capital. However, their classification as “unmanaged” or with specific “potential” indicates a latent vulnerability. These lands represent the very frontiers most susceptible to future conversion, a transition strongly associated with the initiation of soil degradation processes globally14 and identified as a primary driver of ecosystem change worldwide1. The high proportion of stable area, therefore, should be interpreted not as a lack of threat but as a critical window for implementing preventive land-use planning and sustainable management practices to avert future degradation.
Conversely, the mapped unstable areas, though covering a smaller portion of the landscape (7.8%), reveal clear and concerning spatial patterns that are critical for intervention. The predominance of sheet erosion—accounting for the majority (7.04%) of all unstable area—is consistent with global models identifying it as the most extensive form of soil loss by water2,15 and a major contributor to global land degradation1. The spatial correlation of these erosion hotspots with “agricultural frontiers” and interfaces between managed land and natural vegetation underscores a primary driver: land-use transition. This pattern aligns with the classic syndrome of land change where frontier expansion triggers soil degradation14. The resulting soil degradation is a direct consequence of anthropogenic pressure, occurring where natural systems are being modified or where agricultural practices may be exceeding the land’s carrying capacity. Similar intense anthropogenic pressures, notably urbanization and land-use change, are documented as critical factors altering both terrestrial and coastal ecosystems in southeastern Brazil13,16. The concentration of unstable areas in central and peripheral zones highlights specific localities where current land-use systems warrant urgent review. Targeted soil conservation measures, aligned with and reinforcing instruments such as Brazil’s Forest Code17, are most needed in these priority intervention zones.
Discussion of conservation priorities and management implications
The priority classification provides a strategic, multi-tiered framework for directing conservation resources. The finding that over half of the landscape (51.69%) is classified as Stable Medium Priority is significant. This vast area represents lands that are currently stable but possess inherent or contextual vulnerabilities, aligning with the concept of “potential degradation” risk areas that require proactive management to maintain ecosystem services4. Investing in sustainable agricultural practices, agroforestry systems, and compliance with environmental legislation within these zones is a cost-effective strategy to prevent their transition into future degradation hotspots, an approach advocated for in preventative conservation planning18. In the Brazilian context, such preventive measures are central to the implementation of the Forest Code, which aims to protect areas of permanent preservation (APPs) and legal reserves to maintain ecological stability on private lands19,17.
Conversely, the Unstable High Priority areas (4.64% of the total), though smaller in extent, demand immediate and targeted rehabilitation efforts. The concentration of these critical zones at land-use interfaces underscores that degradation is a direct symptom of unsustainable transitions, a pattern well-documented in other global contexts14. The application of the UNEP/PAP/RAC framework in this humid tropical region successfully identified these hotspots, demonstrating its utility beyond the Mediterranean and semi-arid contexts for which it was originally developed (e.g.,5,7. The methodology’s structured integration of biophysical and socio-economic criteria offers a replicable model for translating complex degradation assessments into actionable intervention classes, which is a critical step for operationalizing land degradation assessments20.
This dual-focused strategy urgent rehabilitation of high-priority unstable areas (addressing existing degradation) coupled with the safeguarding of medium-priority stable lands (avoiding future degradation) is essential for achieving LDN targets, which require balancing “losses” to degradation against “gains” from improvement (UNCCD GPG v2, Section 1.4). The resulting priority map directly translates a multi-criteria assessment into a practical blueprint for environmental agencies, enabling efficient, spatially explicit allocation of resources. Such prioritization is fundamental for operationalizing LDN and aligning local actions with national LDN targets and SDG 15.3, as it moves beyond merely calculating the proportion of degraded land to informing where and how to act21. By emphasizing that preventive measures in stable areas are as crucial as rehabilitation in degraded ones, this study supports an integrated land management approach aimed at achieving a land degradation-neutral world.
Discussion of LULC dynamics and degradation linkages
The observed land-use and land-cover (LULC) transitions in the study area from 1985 to 2024 align closely with broader regional dynamics documented in the Atlantic Forest biome and Rio de Janeiro state, where key drivers include agricultural expansion, urbanization, deforestation, and policy-induced recovery. Urban areas expanded dramatically by 203.50 km2 (199.42%), consistent with patterns of metropolitan growth and peri-urbanization across the state, driven by population influx and economic development22. This expansion often converts agricultural mosaics into built-up land, increasing pressure on surrounding rural landscapes. Concurrently, pasture expanded by 14.74% (167.61 km2) while Mosaic of Uses declined by 34.35% (349.49 km2), indicating a process of agricultural intensification and landscape simplification. This widespread trend in southeastern Brazil is fueled by demand for livestock products, where heterogeneous farming systems transition to more homogeneous pasturelands, often operating below their productive potential17. Forest Formation showed a modest net loss of 1.26% (7.02 km2) but exhibited recovery after 1995. This pattern mirrors the slow but positive stabilization and regrowth observed in the Atlantic Forest biome, driven by strengthened environmental legislation such as Brazil’s Forest Code and reduced deforestation23,12.
The qualitative transition analysis presented in Section “Land Use Transition Analysis and Degradation Linkages” provides insights into the relationship between land cover change and observed degradation hotspots. The conversion from Mosaic of Uses to Pasture emerged as a transition pathway frequently associated with unstable areas, particularly in the central portion of the study area. This finding aligns with the understanding that the simplification of heterogeneous agricultural systems into extensive pastureland—often without accompanying soil conservation practices—can increase erosion vulnerability. The sheet erosion features observed in these areas suggest that the process of land conversion itself, rather than the eventual land use alone, may create conditions favorable to soil loss. Similarly, the conversion from Forest Formation to Mosaic of Uses, observed in steeper terrain, highlights the erosion risks associated with forest clearing on vulnerable slopes. This pattern is consistent with global findings that deforestation on sloping lands accelerates runoff and soil loss, particularly during the initial post-clearing period when soil remains exposed2.
The expansion of urban areas at the expense of pasturelands was also associated with degradation features, particularly sheet and localized rill erosion. Soil exposure during construction, compaction from heavy machinery, and alterations to natural drainage patterns collectively contribute to increased erosion risk in peri-urban environments16. Notably, areas that remained under continuous forest cover or underwent natural regeneration appeared to exhibit greater stability, supporting the protective role of vegetation in maintaining soil integrity. This observation reinforces the importance of forest conservation and restoration as strategies for erosion control.
The finding that degradation hotspots are frequently associated with land use transitions—rather than stable land use persistence—has important policy implications. Interventions aimed at preventing degradation should be strategically timed to coincide with periods of land use change, when technical assistance, conservation planning, and soil conservation measures can be most effectively implemented. This approach aligns with the concept of “transition-driven degradation”14, where the process of land conversion creates windows of vulnerability that require targeted intervention. Divergent coastal ecosystem trends were observed: mangrove areas expanded while wetlands contracted. This highlights differential pressures from coastal development and aquaculture versus inland drainage for agriculture. Mangroves appear to have benefited from protective policies and natural expansion,studies in the Rio de Janeiro coastline document mangroves encroaching landward and expanding over salt marshes, often in response to local geomorphological shifts, sedimentation patterns, and relative sea-level rise16,24.
Finally, the emergence of sugarcane and the sharp rise in Other Temporary Crops signal nascent agricultural shifts tied to market demands and climate-adapted cropping in southeast Brazil, including Rio de Janeiro, necessitating ongoing monitoring (Maria25,13.
Limitations and implications for management
This study provides a robust spatial assessment of land degradation and conservation priorities. However, certain limitations should be acknowledged to contextualize the findings.
Validation limitations
Systematic field-based ground-truthing was not conducted following the completion of the classification and mapping phases. To mitigate this limitation, the classification methodology incorporated several quality assurance measures: (1) iterative refinement of training samples using very-high-resolution (
Prioritization framework limitations
The conservation prioritization, while based on a structured multi-criteria framework informed by expert judgment, has certain constraints. Socio-economic variables G (rural exodus), H (land tenure), and I (other aggravating socio-economic factors) were assigned the lowest impact score (1) for all land units because no field survey or questionnaire was conducted. Future applications of this framework would benefit from participatory engagement with local farmers, landowners, and community representatives to capture nuanced socio-economic values, land tenure complexities, and local ecological knowledge, thereby refining the scores for these variables.
Data accessibility limitations
Following the completion of the analysis, access to the geospatial datasets and computational infrastructure was no longer available. Consequently, certain quantitative validations and statistical analyses that would ideally accompany a study of this nature could not be performed. The authors have addressed this by presenting findings qualitatively where precise statistics could not be verified, and by emphasizing the methodological transparency of the approach.
Implications for management
Despite these limitations, the findings offer clear and actionable implications for land management in the State of Rio de Janeiro. The spatially explicit priority map (Fig. 4) serves as a direct decision-support blueprint for environmental agencies at state and municipal levels. It enables the efficient direction of technical assistance, conservation incentives (e.g., payments for ecosystem services), and regulatory enforcement towards the most critical intervention hotspots, particularly the Unstable High Priority areas identified in municipalities such as Rio Bonito and Boa Esperança.
The results advocate for an integrated, two-pronged management strategy essential for achieving land degradation neutrality. This strategy must couple the urgent rehabilitation of high-priority unstable areas with robust policies and incentives that safeguard the extensive Stable Medium Priority lands from future degradation. Investing in sustainable agricultural practices, agroforestry, and adherence to the Forest Code within these stable-yet-vulnerable zones represents a cost-effective, preventative approach to conservation.
By implementing this dual focus, policymakers and land managers can work towards ensuring the long-term ecological functionality and economic productivity of this environmentally significant region.